Which of the Following Is NOT a Function of Protein

Which of the following is NOT a function of protein?

A) Proteins in cell membranes allow transport of water in and out of cells.
B) Enzymes which act as catalysts in biochemical reactions.
C) Antibodies which neutralise foreign proteins and pathogens such as pathogenic bacteria and viruses.
D) Proteins and amino acids can be metabolised to yield energy.
E) Metalloproteins such as transferrin for iron and ceruloplasmin for copper promote absorption of their corresponding minerals.